Unitary magnetic core and condenser



Od. l0, 1950 T. s. BJRKLUND 2,524,754

UNITARY MAGNETIC coRE AND coNnENsER Filed Sept. 5, 1946 2 Sheets-Sheet 1FIG- FIG- 2 I NVEN TOR.

Tom: smvmo BJRKLUND BY Z7 W ATTORNEY Oct. l0, 1950' l 1'. s, BJRKLUND2,524,754

UNITRY4 MGNETIC CORE AND CONDENSER filed sepza 5, 1946 2 sneet-sheet 2FIG. 4

FIG- 6 FIG. 7

INVE/yoR. TORE SIGVARD BJORKLUND WZ/M@ ATTORNEY Patented Oct. 10, 1'950UNI'IARY MAGNETIC CORE AND CONDENSER Tore Sigvard Bjrklund, Stockholm,Sweden, as-

signor to Lumalampan Aktiebolag, Stockholm, Sweden, a corporation ofSweden Application September 5, 1946, Serial No. 695,014 In Sweden June19, 1945 section 1, rubuc Law oso, August s, 194s Patent expires June19, 1965 5 Claims.

This invention relates to ballasts for electric discharge lamp circuits.

Ballasts for the purpose specified have heretoiore been constructed aschokes or transformers providing the discharge lamp circuit with thenecessary series impedance as inductive reactance elements. Howeverit isoften an advantage or even a necessity to have a capacitive reactanceincluded in such supply circuits. In circuit arrangements forfluorescent lamps, for instance, the introduction of condensers hasbeenproposed as means of improving the power factor during the operation.

The object of this invention is to provide a novel form of a ballaststructure in which a capacitive unit designed to correct the powerfactor of the lamp circuit is incorporated with the inductive unit ofthe ballast, the capacitive unit being built up of foils of a magneticmaterial electrically insulated from each other and forming electrodesof a condenser, and the inductive unit being wound upon said condenser.When more than two foils are used they are divided 1 into two groupsforming both the electrodes of the condenser.

This construction possesses the advantage that frame 3 of stampedtransformer sheets fastened by rivets, for instance, into which frame aniron core 5 designed according to the invention is tted. Around the core5 there is the winding 4 of the choke, and the leading-in wires of thewinding are denoted 1. The air gap of the choke is determined by theinsulating discs 2 and t interposed between the core 5 and the ends ofthe frame I. The leading-in wires of the condenser electrodes includedin the core 5 are denoted I.

As shown in Figure 2, the iron core 5 may be 4 produced by winding twoiron foils 8 and III of the power factor correction and thestabilization -I of a lamp circuit is established by means of a singleunit, with consequent simpliilcation of the lamp ilttings.

The invention is illustrated bv a few examples shown in the accompanyingdrawing.

Figure 1 shows a choke designed according to the invention.

Figure 2 shows, on a larger scale, a transverse sectional view taken onthe line 2--2 of Figure 1, of the core for such a choke.

Figure 3 shows schematically a shell transformer designed according tothe invention.

Figure 4 is a transverse sectional view, taken on the line 4-4 of Figure3, and illustrating schematically a core formation for the transformer.

Figures 5, 6 and 7, are transverse sectional views, similar to Figure 4,illustrating the formation of diiferently designed cores.

Figure 8. shows a circuit arrangement for a iiuorescent lamp with achoke designed according to the invention.

The choke according to Figure 1 consists of a suitable thinness whileinserting insulating sheets 9 and Il, which may be of paper, forinstance, into a core of the shape desired, in the ilgure shown with asquare section.

The transformer shown in Figure 3 is provided, in known manner, with acentral leg I3 and is arranged without any air gap. The core is built upof E-shaped sections I2 and Il piled alternately on one another in sucha way that the prongs of one section cover those of the other section.Figures 4-7 show different ways of building up this core, all of whichare practicable in constructing the core 5 shown in Figure 1. Theconstructions are shown with insulating sheets 9 interposed between theiron foils. The condenser layers, or at least one side of eachlayer,.can have, instead, an insulating coat covering the sidecompletely or partially.

In Figure 4 the layer parts I5 and I6 forming the respective condenserelectrodes are piled up alternately in such a way that the prongs of therespective E sections cover one another while the transverse pieces ofthe sections stand out to each side of the transformer. By means of arivet or the like these transverse pieces may be so interconnected as toform, on each side, an electrode of the condenser.

Particularly where thin foils are used it may be found expedient to jointhe sections, as shown in Figure 5, into partial packs I1 and I8, to bealternately piled up as indicated above.

Figure 6 shows how to build up the core shown in Figure 3 of two foils,conveniently stamped, which are folded up into the pack desired.Especially if thin foils are used it may be found expedient to fold themup, as shown in Figure 7, into partial packs 2| and 22 to be alternatelypiled on each other as shown in Figure 5.

It is not necessary to have the transverse pieces of the sectionsstanding out beyond the prongs of the sections as shown in Figures 4-7;the respective layer parts may as well cover one another completely.Where designs according to Figures 4, 5 and 7 are concerned the layerparts may conveniently be provided with salient flaps for purposes ofelectric interconnection. Partial packs, piled or folded, may also beused for designs of wound cores like that shown in Figure 2. In thecircuit arrangement shown in Figure 8 for an electric discharge tube,which in this example is a fluorescent lamp, the electrodes 2l and 2l ofthe discharge tube are connected to the current source across a choke,of which the winding is denoted 2l and the core 24. 'I'he core isdesigned according to the invention as a condenser arranged parallellyto the tube and so dimensioned that the desired improvement of the cos pvalue is obtained during the operation of the tube. In a specimencircuit arrangement tested the choke was made of two-wound layers ofabout 0.009 mm. thickness. Investigations have shown-that the foils areto be made as thin as possible and that for power factor correction theypreferably may be below this thickness. The electrodes 25 and 2l of thetube are shown preheatable at the start by means of a circuit parallelto the discharge path of the tube 2l and including a thermal relay 21with a condenser 2l connected in parallel toit for the regulation of thefunction of the relay 21. The choke included in the circuit arrangementmay be reconnectable, in known manner, to function as a transformerandthus admit operation of the tube at different voltages.

What I claim is: a 1. A ballast for electric discharge lamp circuitscomprising at least one inductive unit wound on a leg of a closed corestructure consisting of a frame of a magnetic material, said leg part ofthe core. structure being built up of a plurality of interfolded thinfoil strips of magnetic material electrically insulated from each otherand forming electrodes of a condenser as a capacitive unit incorporatedwith the ballast and designed to correct the power factor of the lampcircuit. 2. A ballast for electric discharge lamp circuits comprising aninductive unit wound on a leg of a closed core structure consisting of aframe of a magnetic material, said leg crossing the frame between twoopposite sides thereof as a magnetic bridge built up of a plurality ofinterfolded thin foil strips of magnetic material electrically insulatedfrom each other and forming electrodes of a condenser as a capacitiveunit incorporated 4 with the ballast and designed to'oorrect the powerfactor of the lamp circuit.

3. A ballast for electric discharge lamp circuits comprising at leastone inductive unit wound ai a leg of a closed core structure consistingof a frame of a magnetic material, said core structure being entirelybuilt up of a plurality of 'inter-- folded thin foil strips of magneticmaterial electrically insulated from each other and forming electrodesof a condenser as a capacitive unit incorporated with the ballast anddesigned to correct the power factor of the lamp circuit.

4. A ballast for electric discharge lamp circuits comprising at leastone inductive unit wound on a leg of a closed core structure consistingof a frame of a magnetic material, at least said .leg part of the corestructure being built up of a plurality of interfolded thin foil stripsof magnetic material electrically insulated from each other and formingelectrodes of a condenser as a capacitive unit incorporated with theballast and designed to correct the power factor of the lamp circuit,the thickness of said foils of magnetic material not exceeding 0.009 mm.

5. A ballast for electricdischarge lamp circuits comprising atleast oneinductive unit wound on a leg of a closed core structure consisting of aframe of a magnetic material, at least said leg part of the corestructure being built up of more than two interfolded thin foil stripsof magnetic material divided into groups insulated from each other andforming electrodes of a condenser as 'a capacitive unit incorporatedwith the ballast and designed to correct the power factor of the lampcircuit.

TORE BIGVARD BJORKLUND.

REFERENCES crrnn The following references are of record in the ille ofthis patent:v

UNITED STATES PATENTS

